The present invention relates in general to davits that are used to store, launch and retrieve skiffs or rescue boats. In particular, the present invention relates to a SOLAS-compliant, lightweight davit used on a catamaran or a ship to store, launch and retrieve a rescue boat.
Most ships, especially passenger ships, are governed by national and international laws and regulations which are intended to ensure a safe ship, safe operations of the ship and proper registration and use of the ship within national and international waters. The rules and regulations governing international passenger ships include the International Maritime Organization""s (IMO) High-Speed Code (Resolution MSC.36 (63)), the Safety of Life at Sea (SOLAS) regulations, and the Subchapter H regulations for passenger ships, as defined in United States Code of Federal Regulations, 46 CFR.
Since a rescue boat plays a critical role in the emergency evacuation of a ship, the United States Coast Guard (USCG) classifies a davit, which is used to secure, launch and retrieve the rescue boat, as a piece of lifesaving equipment. The design and testing of lifesaving equipment for Subchapter H ships are governed by specific rules and regulations. In particular, the Safety of Life at Sea regulations 13, 14, 15, 16, 20, 47 and 48 of Chapter III, Parts B and C, govern the design of life boats and rescue boats, and the International Maritime Organization""s Resolution A.689(17), Parts 1 and 2, govern testing of equipment.
Accordingly, in order to be SOLAS compliant, a rescue boat davit must be designed to meet at least the following criteria:
1. The davit must not depend on any means other than gravity or stored mechanical power which is independent of the ship""s power supplies to launch the rescue boat;
2. The rescue boat is to be stowed in a state of readiness for launching in not more than five minutes;
3. The rescue boat is to be launchable with the ship making headway at speeds up to 5 knots, in calm water;
4. The rescue boat is to be rapidly recoverable with a full load, including the rescue boat engine, fuel, entrained water, first aid kit and at least six persons;
5. The davit is to be capable of launching the rescue boat against a ship""s trim of 10xc2x0 in either direction and against a ship""s heel of 20xc2x0, in either direction;
6. The davit is to be operable by a single person on the deck of the ship or a single person within the rescue boat;
7. The davit must incorporate safety devices which automatically cut off the power before the davit arms reach the stops in order to avoid overstressing the falls or davits;
8. The davit is to be designed with a factor of safety of 4.5 on the structural components of the davit and the winch and a factor of safety of 6.0 on the falls, suspension chains, links and blocks;
9. The davit must be capable of a minimum lowering speed determined in accordance with the following equation:
S=0.4+0.2H
xe2x80x83where: S is the lowering speed in meters/sec.
H is the height of the davit head above the waterline in meters; and
10. The davit must be capable of hoisting the fully loaded rescue boat at a speed of at least 0.3 meters/second.
Davit systems for storing, launching and retrieving skiffs or rescue boats have been known for some time. Those that are SOLAS compliant, however, are typically fairly heavy and mechanically complex. There is, therefore, a need for a SOLAS-compliant davit system for a weight-sensitive aluminum ship wherein the davit system is lightweight, has a fairly simple mechanical structure, and is easy to operate.
A principal object of the present invention is to provide a rescue boat davit that meets all of the design requirements of the SOLAS, IMO and 46 CFR regulations.
Another object of the present invention is to provide a boat davit that is relatively light in weight and mechanically simple in design.
A further object of the present invention is to provide a boat davit that can launch a rescue boat between the hulls, at the stern, of a SWATH ship or catamaran with forward speed.
A still further object of the present invention is to provide a boat davit that can also permit stern-launching on conventional monohulls.
Another object of the present invention is to provide a boat davit that is xe2x80x9cretrofittablexe2x80x9d onto a fully built, weight sensitive aluminum ship.
The foregoing objects of the invention can be accomplished by a rescue boat davit having a tilting A-frame lifting arm, a winch assembly and an upright post assembly for mounting the winch to the ship. The A-frame lifting arm includes two elongated legs integrally joined at one end thereof to form an apex, and pivotally mounted at the other end thereof to the transom of a ship. The A-frame lifting arm is pivotally moveable between an upright rescue boat stowage position and a lowered rescue boat launching and retrieving position. The A-frame lifting arm also includes a sheave assembly mounted on the apex of the A-frame lifting arm. The winch assembly includes a cable drum and a winch line. One end of the winch line is wound about the cable drum, and the other end is releasably fastened to the rescue boat, with the winch line passing over the sheave assembly to suspend the rescue boat from the apex of the A-frame lifting arm. A boarding platform is mounted to the ship and provides access to the rescue boat when it is in a stowed position.